There are many types of sweeping machines for removing various types of debris from a surface, such as the ground, a floor or a parking lot. Many of these sweeping machines use a rotating cylindrical brush to contact the surface being swept. The rotating cylindrical brush is used to lift various types of debris from the floor or surface and throw it into a debris hopper located near the rotating cylindrical brush. The machine moves the rotating cylindrical brush over the surface being swept. The rotational velocity of the cylindrical brush produces a velocity at the ends of the brush that differs from the velocity of the machine as it moves over the surface being swept. The brush can be rotated in either direction. There are many types of sweepers. Two types of sweepers are forward throw sweeper and indirect throw sweepers. Forward throw sweepers use a brush rotated backward with respect to the travel of the sweeping. The debris is thrown forward and collected in a container which is forward of the brush. Indirect throw or over-the-top sweepers use a brush rotated in either direction with a debris container located for collection of the debris.
Sweeping machines are used in a variety of environments. For example, some sweeping machines remove debris from roads and streets. Others are used to remove debris from parking lots and others are used to remove debris from factory floors. In short, there are many applications for sweeping machines. Sweeping machines also remove different types of debris. Certain brush designs can be employed to enhance a sweeping machine's ability to pick up or remove certain types of debris.
There are several types of brush fill patterns which are customarily used. One predominant type of brush fill pattern is termed full fill or high density. In a full fill type brush the bristles or other sweeping material are closely packed together or in a highly dense configuration. The bristles or other sweeping material of a full fill brush can be placed in almost any type of pattern to form a full fill type brush. The full fill brush presents a substantially solid mass of bristles or other sweeping material. Full fill type brushes are generally effective in removing relatively thin layers of fine material from surfaces being swept. Fine materials, also referred to as fines, include very fine particles, such as sands which are used in foundries for making molds, cement dust, and sand found in parking lots or in streets.
A second predominant type of brush fill pattern has spaces between rows of bristles or other sweeping material. This second type of brush has a number of variations. For example, a brush called a double row brush has two rows of closely spaced bristles or other sweeping material. This is called a double row. There is a larger space between each double row of bristles or other sweeping material. This second type of brush fill pattern is better for removing bulkier debris or deeper layers of fine material.
The second predominant type of brush fill pattern is formed by placing the bristles or other sweeping material in one of several patterns. One pattern is to place the bristles or other sweeping material in straight lines along the brush tube. The straight lines are substantially parallel to the axis of the brush tube. Brushes with straight line pattern of bristles or other sweeping material and spaces between the straight bristles or other sweeping material cause a brush to bounce or jump excessively because as the brush rotates, the brush alternates between having all the bristles or other sweeping material in one row of the brush in contact with the surface being swept and no bristles in contact with the surface being swept. The result of brush bounce is chatter lines of fine debris being left on the surface that has been swept. Brush bounce may also cause vibration of the sweeping machine.
To prevent the brush from bouncing, the rows of bristles are placed in spiral patterns along the surface of the brush tube. The spiral pattern has a number of spiral tufts placed in a pattern with spaces between the spiral pattern of tufts of sweeping material. When the tufts and spaces are in a spiral pattern, the amount of brush material in contact with the surface being swept is substantially constant as the brush rotates so as to minimize the amount of brush bounce. In other words, at any rotational position of the brush, there is always some brush fill material in contact with the surface being swept to support the brush as it rotates. Spiral pattern brushes also have a problem. Debris or fines may travel along the length of the brush. The spiral pattern having spaces between the spirals acts as an auger that may move the debris or fines in one direction along the surface of the brush. This can be a disadvantage since some debris or fines may be augured out at one end of the brush.
To prevent fines and debris from traveling along the length of the brush, many brush designs use a single or double herringbone pattern to break up the auguring effect. The herringbone pattern may also be termed a chevron pattern or may be termed as alternating spirals. These herringbone patterns prevent the migration of debris and material being swept from being augured down the length of the brush. The herringbone pattern allows material being swept to only travel to the point where the spiral changes directions. As a result, these types of brushes are more effective at sweeping up certain types of debris and preventing the auguring along the entire length of the brush during rotation.
Herringbone type brushes do auger debris a certain length. The herringbone patterns can be thought of as using one full chevron or a multiple of one full chevron. One full chevron will have a first spiral in a first direction and a second spiral in a second direction. Brushes which do use the herringbone patterns auger debris along the length of the spiral until the spiral changes directions. The problem with a pattern of brush which has a number of full chevrons or an the same number of different direction spirals is that at both ends of the cylindrical brush, the debris or material being swept will be either augured outward or inward from the end of the cylindrical brush. The direction of auguring is dependent on the orientation of the chevrons with respect to the rotational direction of the brush. It is desirable to rotate the brush so that the debris and fines auger toward the middle of the brush. However, if the chevrons on the brush are always oriented one way, the bristles or brush material forming the brush can take a set. In other words, like a push broom, the bristles or brush material can bend over and become less effective. To prolong the life of a cylindrical brush, regular maintenance requires that the brush be switched or flipped end to end to change the orientation of the chevrons and prevent the bristles or other sweeping material or brush fill material from taking a set in one direction. Flipping the brush end to end changes the direction of the force on the tufts or bristles of the brush. When flipped or switched, the chevrons of the cylindrical brush will auger debris toward both ends of the brush which increases the possibility of trailing. Trailing is where some amount of debris or fines is left at the ends of the brush after the sweeping machine has passed.
Auguring of fines or other debris is troublesome when you consider that many times much of the debris is located on one end of the brush. For example, in streets it has been found that the vast majority of the debris and fines are located on one end of the brush, mainly near the curb and in the gutter. In this instance, there is a need for a cylindrical brush for use on a sweeping machine that will auger the fines or other debris inward toward the center of the brush while it is rotating no matter what orientation of the brush fill pattern of the cylindrical brush. There is also a need for a cylindrical brush that will prevent the material being swept from traveling along the entire length of the brush. There is also a need for a brush that will auger the debris or fines being swept in toward the center of the brush from a selected or desired side of a sweeping machine even when the brush is flipped end-for-end and the brush fill material is re-orientated. For example, it is necessary to have a brush that will auger the material being swept inward despite whether it is in a first orientation or whether it has been flipped end-to-end to a second orientation for maintenance purposes. There is also a need for a sweeping brush that will consistently pick up varying types of debris on a variety of surfaces and one that limits axial migration of debris toward the ends of a rotating cylindrical brush. There is also a need for a brush that minimizes trailing. There is a further need for a sweeping machine that is smooth and stable during its operation.